Semi custom M70 fwt 280 em. when zeroed it shot a 5 shot group that was sub half MOA. took it home and cleaned it thoroughly. took it back to the range today and the first shot was 6 inches low and 3 inches left. next two shots were and 2 inches left of center and dead center vertically. next shot was an inch further right adn an inche higher. the next several shots were dead center adn 2 inches high. Right where the original zero was. all I can think of is that the rifle likes to be dirty
Been there, done that.
Your barrel is shot out.
I suggest either a new barrel, or if this one used to shoot well, you can have a smith set it back a thread or two and cut a new throat. Regardless, you are near the point where no matter how many fouling shots you fire it won't group.
